Trafficking people across international frontiers is a growing problem. Experts say the practice is motivated by two factors: demands for exploitable labor and a predatory global sex industry.

Experts on human trafficking say no country is immune to the problem, and some of them do too little to combat it. Younger women and children are in growing demand by the sex industry, and people are crossing from one continent to the next to fill poorly paid jobs.

The co-executive director of the Coalition Against Trafficking in Women, Dorchen Leidholdt, says human trafficking is driven by the huge demand of the sex industry, and curbing the demand is key to reducing the supply.

"Demand is the weak link in the sex industry chain,? Ms. Leidholdt said. ?There is no question about that. Unlike the women and girls in prostitution, the men and boys who buy women and girls in prostitution have choices to make. They very often have standing in their communities, they have families, they are very responsive to that bright light exposing their activities, to stigma and shame, and if they are subjected to criminal sanctions, we are going to see demand dropping and that is going to make a big difference. It means that fewer women and girls are going to be subjected to this horrible form of slavery."

Ms. Leidholdt spoke at a recent conference at Rome's Gregorian University organized by the U.S. Embassy to the Vatican.

She says pornography and the promotion of the sex industry have increased with advances in technology and the Internet, which makes information readily available to consumers and permits instant and nearly undetectable transactions.

The chair of Women's Studies at the University of Rhode Island, Donna Hughes, says more than half the victims trafficked internationally fall prey to the commercial sex trade. She, too, agrees enforcement must concentrate on the demand side of the human-market equation.

"The most effective way to combat the problem is to criminalize the demand, that is to make buying a sex act a crime, that is to criminalize pimping of women, it means criminalizing brothel-keeping, criminalizing trafficking of women, the recruiting of them and bringing them into countries for prostitution. All of those activities have to be criminalized," Ms. Hughes explained.

Ms. Hughes says trafficking occurs because criminals take advantage of poverty, unemployment and a desire for better opportunities. She says the trade is flourishing because the criminal organizations are getting away with it and making a lot of money.

She told the conference human trafficking could not take place without the complicity of corrupt governments.

"Corruption of government officials and police is necessary for trafficking and exploitation of large numbers of women and children,? Ms. Hughes. ?In sending countries large-scale operations require collaboration of officials to obtain travel documents and facilitate the exit of women. In destination countries, corruption is an enabler for prostitution and trafficking."

Ms. Hughes says some governments' indifference to the problem contributes to the growth of demand for child pornography and prostitution.

The United States keeps track of countries that do too little to combat human trafficking. Among the 10 worst countries are Equatorial Guinea, Sierra Leone, Sudan, Bangladesh, Burma, Ecuador, and Venezuela.

In its most recent report on the subject, the State Department said several European and former Soviet republics have stepped up their efforts to curb the illicit human trade. They include Bosnia-Herzegovina, Georgia, Kazakhstan, Turkey, and Uzbekistan.

Ms. Leidholdt says the underground nature of human trafficking makes it very difficult to get accurate numbers about just how many people are involved.

"In terms of numbers of victims, the United Nations says four million people are trafficked annually. Interpol has estimated that traffickers reap $19 billion a year. The numbers are huge and the numbers are growing," Ms. Leidholdt added.

Ms. Leidholdt says one country that must be held up as an example of how trafficking should be combated is Sweden, where in the mid-1990s officials recognized that the way to cut down on the lucrative human-trafficking activity is to reduce the demand.

The Swedish government eliminated criminal penalties against women and girls in prostitution and improved services for their rehabilitation, while at same time imposing severe penalties on traffickers and buyers. It also carried out an intense public education campaign to inform the public about the dangers of human trafficking.

Ms Leidholdt says the result was a dramatic drop in prostitution and a significant decline in sex trafficking. She says other countries should do the same.

The United Nations says human trafficking is the third-largest criminal enterprise worldwide, and urges governments to intensify their efforts to put traffickers of human beings out of business.